Strange electronic behavior...

[RJK]

Hi folks-I got my Z out this morning for a drive, and had a strange experience. car started the drive exactly as expected, with gauge readings exactly as expected. about 15 minutes in, I turned the fan on. almost immediately, my alternator gauge jumped from middle-ish to peg all the way to the right. car started to stumble, and stalled out. i had to keep my revs in the 2k range to get to my location without stalling out more. turning the fan off, it crept back towards middle point, SLOWLY. got to my destination. 2 hours later, i left(no fan on this time). alternator gauge looked normal-ish at first, but then started to get jittery, and be in the 13-14V range. had some more stall outs at lights, and had to ride the throttle when stopped. my specs:

1972 240Z. new battery, new alternator, MSD ignition upgrade. 5 new plugs last year(I found that one had been helicoil-ed at one point, and couldn't find the right sleeve), one old plug. this wasnt a problem before.

 

any thoughts as to what is happening here? thanks!

[Patcon]

Do you have a volt meter?

Check battery voltage with car off and then with the car running. Post those numbers...

[SteveJ]

This can be useful for early Z cars that don't have a voltmeter: https://www.amazon.com/gp/product/B01M9IKYVH

Did the fuse for the fan survive this event? It about sounds like you might have a short in that circuit.